Liquid bleaches have long been used in households as aids in the bleaching and cleaning of fabrics. Hypochlorite bleaches have been used most extensively for this purpose since they are highly effective, inexpensive and simple to produce.
In an attempt to broaden and extend the utility of bleaches for household use, other bleach systems have been introduced in recent years. Prominent among these are dry powdered or granular compositions, most usually based upon peroxy- compositions or perboro- compositions. Such materials must be placed into aqueous solution to release the active bleaching agents.
Liquid bleaching compositions including peroxy compounds have generally been utilized less in the household market than the solid forms referred to above. Although hydrogen peroxide compositions effectively bleach a broad range of fabric materials, are less harsh than hypochlorite bleaches and do not release objectional gases or odors, they have not found as much use in the household market as hypochlorite bleaches. This lack of use in the household market has been partially attributable to the instability of peroxide solutions. Instability is mediated principally by metal ion contamination even in extremely low concentrations. Considerable effort has been expended in the search for stabilizing agents for hydrogen peroxide compositions.
Perhaps one reason why stabilized hydrogen peroxide compositions have not been successful is the fact that it is very desirable to add other organic components to commercial bleaching compositions, especially where the compositions are intended to be used as "pre-spotters". Such "pre-spotter" compositions most advantageously include surfactants for their detergent effect, fluorescent whiteners (also known as optical brighteners) to increase fabric reflectance and the user's perception of increased whiteness, and dyes for producing a pleasing color to the bleach solutions. All of the above components, in addition to the bleach compounds themselves, have been found to be necessary in a liquid peroxygen bleaching composition to achieve full acceptance in the household market.
Unfortunately, liquid bleaching compositions based upon peroxide not only deteriorate from the presence of contaminants, e.g., trace metal cations (0.5ppm or greater); in addition, the surfactant, fluorescent whiteners and dyes are attacked by the peroxide itself, as it is a powerful oxidizing agent. Thus, peroxide based bleaching compositions including surfactants, fluorescent whiteners and dyes deteriorate quite rapidly. The surfactants are oxidized and lose their detergency; the fluorescent whiteners are oxidized and lose their effect; and the dyes are oxidized and lose their color or are changed to undesirable colors.